1. Field of the Invention
The invention relates generally to the field of electrical communications. More specifically, the invention relates to acoustic wave systems and devices. In greater specificity, but without limitation thereto, the invention relates to an underwater signal transducer apparatus having an electrically driven, constrained diaphragm.
2. Description of the Related Art
Underwater communication is commonly made through acoustoelectric signal transducers. Typically, these transducers are acoustic loudspeakers housed within watertight and pressure resistant enclosures. Operation of these loudspeakers produces air perturbations within the transducer enclosure, which are in turn passed to a resilient membrane or diaphragm that covers an open part of the enclosure. The diaphragm serves to transmit these air perturbations to the underwater medium.
In the past, generally spherical diaphragms have been incorporated with some underwater signal transducers. These spherically configured diaphragms have been considered to be particularly desirable for sonar applications requiring axially symmetric wave front patterns. Yet, air-filled, spherically configured diaphragms have been known to migrate due to buoyancy, oftentimes rupturing in the process. Further, in cases in which the inflatable spherical diaphragm has been used, the inherent resiliency of this diaphragm has contributed to low resonant frequency, low impedance and low quality factor as well as a large bandwidth of the transducer system. Additionally, transducer systems utilizing this type of diaphragm have been known to have relatively low acoustic source levels, as transducer power requirements are high in relation to appreciable sound transmission.